Unnest the nested list [[1, 2], [3, 4]] recursively into separate rows.
```sql
WITH RECURSIVE unnest_list AS (
    SELECT 1 AS level, array[[1, 2], [3, 4]] AS data
    UNION ALL
    SELECT level + 1, UNNEST(data) AS data
    FROM unnest_list
    WHERE level < 2
)
SELECT value
FROM unnest_list,
LATERAL FLATTEN(input => data) AS t;
```
```sql
WITH RECURSIVE unnest_list AS (
    SELECT 1 AS level, array[[1, 2], [3, 4]] AS data
    UNION ALL
    SELECT level + 1, UNNEST(data) AS data
    FROM unnest_list
    WHERE level < 2
)
SELECT value
FROM unnest_list,
LATERAL FLATTEN(input => data) AS t;
```